Metallurgical melting amd refining process



March 12, 1968 E. F. KURZINSKI METALLURGICAL MELTING AND REFININGPROCESS '7 Sheets5heet 2 Original Filed April 5, 1961 INVENTOR. EDWARDF. KURZINSKI A TTOR NE Y S March 12, 1968 E. F. KURZINSKI METALLURGICALMELTING AND REFINING PROCESS '7 SheetsSheet 5 inal Filed April 5, 1961Orig,

INVENTOR. EDWARD F. KURZINSKI ATTORNEYS March 12, 1968 E. F. KURZINSKI"METALLURGICAL MELTING AND REFINING PROCESS 7 Sheets-Sheet 45 OriginalFiled April 5. 1961 INVENTOR.

EDWARD F KURZI NSKI A TTORNEYS March 12, 1968 E. F. KURZINSKIMETALLURGICAL MELTING AND REFINING PROCESS 7 Sheets-Sheet Original FiledApril 5. 1961 INVENTUR. EDWARD F. KURZINSKI MiG J ATTORNEYS March 12,1968 E. F. KURZINSKI METALLURGICAL MELTING AND REFINING PROCESS '7Sheets-5heet u Original Filed April 5, 1961 JNVENTOR. EDWARD F.KURZINSKI A TTORNEYS March 12, 1968 E. F. KURZINSKI METALLURGICALMELTING AND REFINING PROCESS 7 Sheets-Sheet Original Filed April 5. 1961w N T Z N R E U V K W F D R A W D E /1 i /x ATTORNEYS United StatesPatent 26 364 METALLURGICAL MELTING AND REFINING PROCESS Edward F.Kurzinski, Doylestown, Pa., assignor, by mesne assignments, to AirProducts and Chemicals, Inc., Trexlertown, Pa., a corporation ofDelaware Original No. 3,194,650, dated July 13, 1965, Ser. No.

101,022, Apr. 5, 1961, which is a continuation-in-part of Ser. No.7,457, Feb. 8, 1960. Application for reissue June 21, 1966, Ser. No.562,976

27 Claims. (Cl. 75-43) Matter enclosed in heavy brackets 3 appears inthe original patent but forms no part of this reissue specification;matter printed in italics indicates the additions made by reissue.

This application is a continuation-impart of applicants copendingapplication S.N. 7,457, filed February 8, 1960 (and now abandoned), forMetallurgical Process and Apparatus, which application is acontinuationin-part of application SN. 804,809, filed April 7, 1959, forSteel Making Process, now abandoned.

The present invention relates to improvements in metallurgical processand apparatus and more particularly to novel methods and apparatus forproducing metals in furnaces of the type in which material is placed ina furnace and heat is applied to the material by a flame which impingeson the material.

The production of metals in furnaces of this type requires, among otherthings, controlled application of heat to the furnace including rapidapplication of the greatest permissible quantity of heat to the materialwhile maintaining a proper atmosphere within the furnace during variousstages of a heat, such as the meltdown period, the period of hot metaladdition and the working or refining period.

The present invention is applicable to a variety of furnaces for theproduction of a variety of non-ferruginous metals. Problems overcome bythe present invention, however, can for the most part be illustrated byreference to the production of. steel in an open hearth furnace, itbeing expressly understood that this is only one of the many examplesthat could be cited. In a conventional open hearth furnace, heat issupplied by combustion of fuel in burners fixed in the end walls of thefurnace. The quantity of heat that may be introduced into a furnace inthis manner is limited by the roof refractories and by the furnacegeometry, the roof refractories being damaged by high temperature andthe furnace geometry limiting the amount of air that can be supplied,and thus correspondingly limiting the quantity of fuel that can beburned and the size and shape of the flame. Moreover, a substantialproportion of the heat transfer from the burner flame is by radiation tothe material in the hearth. Naturally, the heat from the flame isradiated in all directions from the flame, and only that portion of theenvironment of the flame which is occupied by the charge is thus heatedby the flame: and if the charge is covered with slag, it is the slag andnot the charge that receives the heat directly from the flame.

Attempts have been made in the past to increase the transfer rate ofheat units to the material in the hearth such as by the use of multipleburners fixed in the end walls or in the roof or by the use of highdensity fuels. In all such cases, however, an inefficient performanceresulted since the fuel input was materially limited by the maximumpermissible roof temperature, since there was inefficient heatinterchange between the burner flames and the material in the hearth.and since the heat insulation characteristics of the slag interferedwith heat transfer to the charge.

Comparable difiicultics have been encountered in other types ofpyrometallurgical apparatus and processes of the general types recitedabove.

ice

Accordingly, it is an object of the present invention to provide novelmethods of and apparatus for improving the efficiency of heat transferto material comprising the charge of a metallurgical furnace.

Another object of the present invention is the provision of a novelmethod of and apparatus for transferring heat to material in ametallurgical furnace in such a manner as to permit an increase in thefuel input to the furnace without damage to the furnace.

Still another object is to provide a novel method of and apparatus foroperating opcn hearth furnaces which results in a drastic reduction inthe time for a heat as compared to the heat time required whenpracticing cOnventional methods.

During stages of a pyrometallurgical process in which the charge isexposed to flames, it may be necessary, due to normal or abnormalconditions, periodically to vary the heat units supplied to the materialunder treatment. For example, during hot metal addition, a foaming slagmay form which further decreases the heat conductivity between the flameand the bath and as a result the bath becomes cold and sluggish. Thiscondition presents a serious problem in conventional furnace operationand it is necessary to decrease the fuel input to the furnace in orderto maintain the temperature of the lining within safe limits, therebyslowing down the process until a normal slag is obtained. Also, controlof heat to the bath is required during the working or refining stage ifmetallic ores are added to the bath to supply oxygen to the reaction,since the addition of orcs reduces the bath temperature at a time whenthe bath must be at a temperature sutlicient to prevent freezing uponaddition of the oxidizing agents and also to promote the endothermicoxidizing reactions involving the metallic ores. Also, difficultiesresulting in time-consuming operations are also experienced inconventional practice when attempting to obtain and maintain proper bathtemperature and furnace atmosphere so as to assure the desiredcomposition of the bath at the time of tapping.

It is therefore a further object of the present invention to provide anovel method of and apparatus for accurately controlling and varying thetemperature of a furnace of the type described.

A still further object of the present invention is the provision ofnovel methods of and apparatus for controlling the atmosphere of afurnace of the type described during various stages of the process.

Further objects and features of the present invention will becomeapparent from a consideration of the following dcscription, taken inconnection with the accompanying drawings, which illustrate severalembodiments of the present invention. It is to be understood, however,that the several embodiments of the present inven tion shown in theaccompanying drawings are by no means all the embodiments of which theinvention is susceptible.

In the drawings, in which similar reference characters denote similarelements throughout the several views:

FIGURE 1 is a diagrammatic view, partially in longitudinal section, ofone end of an open hearth furnace constructed in accordance with oneembodiment of the present invention;

FIGURE 2 is a plan view, partly in section, of the structure shown inFIGURE 1;

FIGURE 3 is a detailed view of a portion of the apparatus shown inFIGURE 1;

FIGURE 4 is a diagrammatic view, partly in longitudinal section, of anopen hearth type of furnace modified in accordance with anotherembodiment of the present invention;

FIGURE 5 is a view in horizontal section taken on the line 5-5 of FIGURE4;

FIGURE 6 is an enlarged view in cross section of the discharge end of ajet device according to the present invention;

FIGURE 7 is a view in cross section of a modified open hearth furnaceaccording to the present invention;

FIGURE 8 is a diagrammatic view, partly in section, of a furnaceconstructed in accordance with still another embodiment of the presentinvention;

FIGURE 9 is a diagrammatic view, partly in section, of furnace apparatusconstructed in accordance with further embodiments of the presentinvention;

FIGURE 10 is a diagrammatic view, in section, of a furnace constructedin accordance with a still further embodiment of the present invention;and

FIGURE 11 is a plan view, partly in section, of the apparatus of FIGURE10.

In general, the present invention comprises conducting fuel and oxygenwithin a furnace along at least one confined path to a point in thefurnace spaced from the walls of the furnace and in close proximity tomaterial in the furnace and there forming a high temperature highvelocity flame which is impinged directly on adjacent material fromabove and from only a short distance away. During the melting downperiod, the flame is played on the material within the furnace. When theinvention is practiced in connection with a liquid charge, as for example during the refining period following a melting down period, theflame is directed against the charge from a short distance away and theaxis of the flame is maintained at an angle greater than with the chargeand the flame is given such a velocity as to part any slag that may beon the surface of the liquid charge so that the flames directly contactthe molten metal. In any event, this method differs fundamentally fromthe earlier methods in that heat is transferred from the flame to thecharge (e.g., pig iron) whether solid or molten, substantially byconvection rather than by radiation. In particular, it has been foundthat the temperature gradient across the flame of the present inventionis less than for conventional practice using air, or for that matterless than conventional burner practice employing oxygen with air, sothat in eflect the proportion of the flame contacting the charge whichis at or near the maximum flame temperature will be considerably greaterthan in conventional practice; While at the same time, the surface areaof the flame from which radiation can take place is greatly reduced ascompared to conventional practice. As a result, the rate of fuel feedand hence the rate of heat input can be increased, and the total time ofthe heat can be reduced, compared to conventional practice.

Referring now to the drawings in greater detail, one of the manyembodiments of the present invention is shown in FIGURES l, 2 and 3 inthe environment of a generally conventional open hearth furnace whichhas been modified relatively little to adapt it to the practice of thepresent invention. As is there shown, an open hearth furnace isprovided, including a bottom 10, a back wall 11, a front wall 12, an.end wall 13, a roof 14 and a roof port 15, illustration of only one endportion of the furnace being necessary for an understanding of theprinciples of the invention. The bottom 10 provides a hearth 16 incommunication with a port 17 which leads through gas passageway 18 toconventional checkers (not shown). A conventional end wall burner 19mounted in end wall 13 and fed with fuel and steam such as liquid fuelatomized by steam. When burned with air heated in the checkers, the fuelproduces a flame 20 which is directed longitudinally of the furnace ontomaterial in the hearth such as a solid charge, or a bath of moltenmaterial 21. Burner 19 has the usual means (not shown) for feeding andejecting combustible fuel mixtures. There is an iden tical burner at theother end of the furnace (not shown), and the burners are operated inalternation, as is usual. The structure thus far described isconventional.

In order to change the mode of heat transfer and to achieve the objectsof the invention, the present invention provides, in connection withthis first embodiment, a novel method of and apparatus for introducingfuel and oxygen into the furnace through at least one confined path to apoint in the furnace spaced from the roof and walls of the furnace andabove the charge, and there forming the fuel and oxygen into a highvelocity high temperature flame which is relatively small compared to aconventional burner flame and which is impinged directly onto materialin the hearth in close proximity therewith, so that heat is transferredto the charge substantially by convection rather than by radiation. Forthis purpose, there is provided an elongated jet device 25 positioned inthe end wall 13 of the furnace by mounting means 26 which permitsuniversal movement of the jet device including rotation about itslongitudinal axis. Jet device 25 is slidable through mounting means 26and is thus movable along its own axis relative to the furnace. Theelongated jet device includes a discharge end 27 located within thefurnace and which may be angular-1y disposed with respect to theiongitudinal axis of the jet device, and an input end 28 located outsidethe furnace. Jet device 25 is disposed below burner 19 and extends intothe furnace substantially beyond burner 19 so that the flame from burner19 masks the flame from jet device 25 from the roof. A similar jetdevice is located in the opposite end wall of the furnace, beneath theend wall burner in that end wall. The jet devices, like the end Wallburners, may be alternately operated in synchronism with the directionof flow of air to and exhaust gases from the furnace Apparatus foruniversally moving jet device 25 includes a sleeve 30 universally joinedas by a ball and socket arrangement 31 to the upper end of a verticallydisposed pedestal 32 screw threadedly mounted in a supporting base 33provided with a movable member 34 operable to establish the height ofpedestal 32, the member 34 being shown in the form of a hand wheel formanual adjustment. Supporting base 33 i mounted on t ansverse track 35and the transverse track is in turn slidably mounted on a pair oflongitudinal tracks 36 supported on floor 37. Base 33 may be movedrelative to track 35 and track 35 may be moved relative to tracks 36 bysuitable power means (not shown) and these members may be locked in anydesired position relative to each other by means of pins 38. With thisarrangement, movement of the transverse track relative to thelongitudinal tracks will effect inward and outward movement of thedischarge end of the jet device relative to the end wall, and movementof base 33 relative to the transverse track will cause the jet device toswing toward the front wall or the back wall of the furnace dependingupon the direction of movement of the supporting base. Verticaladjustment of pedestal 32 will effect vertical movement of the dischargeend of the jet device relative to the hearth. The device may be rotatedabout its longitudinal axis to move the discharge end 27 to differentangular positions by employing a split sleeve 30 provided with clampingmeans 39.

Jet device 25 is of. the cooled type and includes longitudinalpassageways (not shown) extending from inlet end 28 to at least adjacentdischarge end 27, for conducting a cooling fluid such as water throughinlet conduit 44 to the discharge end 27 and for returning warmedcooling fluid to the inlet end of the device for discharge throughoutlet conduit 45. In addition, the jet device includes structuredefining a pair of conduits, each formed by at least one passageway (notshown) extending from the input end 28 to the discharge end 27. Thedischarge end of the jet device thus provides means for mixing the fueland oxygen and for discharging the mixture for combustion in thefurnace. One of the passageways is fed with oxygen controllably suppliedby conduit 42 having control valve 43 and another confined path receivesfuel in gaseous or liquid form supplied through conduit 40 provided witha control valve 41. When liquid fuel is used, gaseous oxygen may be usedto atomize the fuel and the atomization may be accomplished in oradjacent the discharge end 27. Whether the fuel is in liquid or gaseousform, the mixing with the oxygen may be performed at or near thedischarge end of the jet device or outside the furnace such as at theinlet end 28. In the latter case, the jet device may include but onepassageway for feeding the combustible mixture through the jet device toits discharge end. Obviously, however, the combustible mixture isexplosive when confined; and hence, Well-designed equipment is neededwhen mixing upstream from the discharge end. Thus, jet device 25 may forexample comprise three concentric shells; an inner passageway throughwhich fuel passes, a middle passageway surrounding the inner passagewayand through which oxygen passes, and an outer passageway for water, theouter passageway being closed at discharge end 27 and dividedlongitudinally into two separate passageways except at end 27, so thatwater must pass down to end 27 and back when traveling from conduit 44to conduit 45. The inner and middle conduits, of course, are open at end27.

The embodiment of FIGURES l, 2 and 3 has the advantage that it isadaptable to existing installations such as present day open hearthfurnaces for steel production. In accordance with the principles of thepresent invention, however, it will be evident that a relatively highproportion of the fuel supplied to the process should be fed through thejet devices rather than through the end wall burners. Nevertheless,there remains a certain advantage in continuing to supply some of theheat requirements of the process by means of the end wall burners ratherthan entirely through the jet devices, for the relatively lowtemperature flames from the end wall burners form in effect a canopyover the relatively high temperature flames of the jet device, so thatthe roof refractories are not subjected even to the relatively smallquantity of high temperature radiation which is nevertheless emittedfrom the high temperature fiames notwithstanding the fact thatsubstantially all the heat from these flames is transmitted byconvection to the charge. Thus, although the principal source of heat inthis embodiment in the present invention is the jet flames, the canopyeffect of the end wall burner flames and the resulting transmission tothe charge of heat that might otherwise be lost by radiation from thejet flames may often make it economically feasible to continue tooperate the end wall burners at reduced rates of fuel consumption.

The concept of the present invention of conducting fuel and oxygen towithin a furnace along at least one confined path to a point in thefurnace spaced from the walls of the furnace and in close proximity withmaterial in the furnace and there forming a high temperature flame whichis impinged directly on the material may, in accordance with anotherembodiment of the present invention, be employed in conventional openhearth furnaces in a manner different from the embodiment shown inFIGURES l, 2 and 3 which makes it possible to operate conventional openhearth furnaces according to a novel process providing greatly improvedproduction even though the major portion of the total fuel input of thefurnace may be introduced through the conventional end wall burners. Insuch an embodiment one or a plurality of elongated oxy-fuel burners orjet devices are mounted in the roof of a conventional open hearthfurnace with the longitudinal axis of the oxyfuel burners, substantiallyvertically disposed by an apparatus which permits vertical adjustment ofthe discharge ends of the oxy-fuel burners within the furnace. AlthoughFIGURES 4 and 5 of the drawings illustrate a still further embodiment ofthe invention to be described in detail below, the figures show themanner oxy-fuel burners may be mounted in the roof of a conventionalopen hearth furnace. The roof 53 of the furnace of FIGURE 4 may beconsidered as the roof of a conventional open hearth furnace and aplurality of elongated jet device or oxy-fuel burners 59 are mountedthrough the roof 53 for heightwise adjustment within the furnace. FIGURE4 illustrates two elongated oxy-fuel burners in one half of the furnaceand therefore this drawing shows an arrangement including four oxy-fuelburners mounted in the roof of the furnace. It is to be understood thata greater or lesser number of oxy-fuel burners may be employed ifdesired. The oxy-fuel burners 59 extend through mounting means 61 in thefurnace roof to within the furnace for heightwise movement relative tothe furnace roof and means are located without the furnace foradjustable positioning the oxy-fuel burner within the furnace; a rack 63on the jet device cooperating with a pinion located within stationarysleeve 67 and manipulated by a hand wheel 65 may be provided for thelatter purpose. The oxy-fuel burners may include a single axiallydisposed nozzle at their discharge ends but it is preferable to employelongated oxy-fuel burners having discharge ends in cluding a pluralityof nozzles inclined outwardly from and substantially equally spacedabout the longitudinal axis of the burners. The oxy-fuel burners 59,like the jet device 25 of FIGURE 1, are provided with oxygen and fuelpassageways which communicate outside the furnace with sources of oxygenand fuel through suitable valved conduits. The passageways extendthrough the elongated burners and by means of a suitable mixingarrangement a combustible mixture is discharged through the nozzles andburned in short, high intensity flames extending angularly anddownwardly from the discharge ends of the oxy-fuel burners. The oxy-fuelburners 59 are also fed with suitable fluid coolant. Oxy-fuel burnersdisclosed in applicant application Serial No. 101,012, filedconcurrently herewith, may be used in connection with the presentinvention.

In operation of a conventional open hearth furnace modified to includeone or more roof-mounted oxy-fuel burners as described above, theoxy-fuel burners are moved upwardly ina direction toward the roof of thefurnace and fuel and oxygen is fed to the oxy-fuel burners to providehigh intensity, relatively short, flames directed downwardly into thefurnace, and the end wall burners are fired and the furnace is reversedgenerally in the usual manner, however, the oxy-fuel burners, when inoperation, are independent of furnace reversal. The charging of solidmaterial is initiated before or after the oxy-fuel burners are fired andthe oxy-iuel burners are adjusted heightwise so that the high intensityflames impinge directly onto the solid material, the position of theoxy-fuel burners being adjusted as required upon melting of the solidmaterial. The foregoing operation continues until the charging of solidmaterial is complete. For maximum efilcierlcy and temperature theoxyfuel burners should be adjusted hcighlwise to position the inner coneof the flame as close as possible to the charge as permitted byconditions of melting, temperature of the charge, size of area of chargedirectly affected by oxy-fuel burner flame and metal splash. Aftercompletion of the solid charge and banking of the furnace doors, hotmetal is added to the furnace; fuel to the oxy-fucl burners being cutoff prior, during or after the hot metal additions depending uponconditioning within the furnace. Immediately after the hot metaladditions the oxy-fuel burners may be lowered to within several inchesabove the bath and then oxygen alone is discharged through the nozzlesonto the bath to effect the required refining of the metal. During therefining period the heat input to the furnace may be reduced bydecreasing the fuel input to the end walls burners or if additional heatis required fuel. may be fed to the oxy-fuel burners.

The foregoing process results in a material decrease in the timerequired for a heat. that is the period between the beginning of thesolid charge and tapping. The re duced time of the heat is achieved bythe t" of oxyfuel burners which function to transfer rapidly into thecharge an extraordinary large quantity of heat units. However, theremarkable reduction in heat time does not result merely from a morerapid melting of the solid charge which would be expected as aconsequence of the additional heat input but from unobvious resultingfactors which makes it possible to adopt novel opera ing procedures. Inparticular, the novel process permits the hot metal addition to be madeimmediately after com pletion of the solid charge and obtains asubstantial reduction in the refining period as compared to conventionalopen hearth practice employing oxygen.

In spite of the fact that substantially greater heat has been introducedinto the furnace and absorbed by the material in the furnace during thecharging pezlod, as compared to conventional practice, at completion ofthe solid charging the material within the furnace has not reached thecondition necessary in normal practice for the hot metal addition. Thus,by practicing this cmbodiment of the present invention the charging timeand melt down time of conventional practice has been redueed to the timerequired to complete the solid charge. The novel process thereforeincludes, in addition to the unique manner of introducing heat to thematerial within the furnace through the ()Xy-fLlCl burners, the step ofadding hot metal after completion of the solid charge at a time when thetemperature of the charge is non-uniform (the portions of the chargeimpinged upon by the high intensity flames from the oxy-fuel burnersbeing at a higher temperature than portions of the charge removed fromdirect influence of the burners) and before the charge attains asubstantially uniform temperature which is the condition existing whenhot metal is added according to conventional practice.

While the greatest efficiency will be realized by adding hot metal assoon as possible after completion of the solid charging it will beappreciated that delays may exist between completion of the solid chargeand hot metal addition. Such delays may be occasioned by required mechanical adjustment of equipment, such as the necessary banking of thefurnace doors before hot metal additions. or may exist merely because aspecific schedule of operation has been arbitrarily adopted. In anyevent, if the hot metal is added after completion of the solid chargebut before the temperature of the charge becomes substan tially uniform,such as the required condition of the charge for hot metal additionunder conventional practice, substantial savings in time are obtainableand it is to be understood that the present process embraces suchdelayed hot metal additions.

A 200 ton open hearth furnace was operated according to the foregoingprocess producing several heats and the average time between the startof the charge and the tap was about three hours considering unrelateddelays due to mechanical difficulties; the period between the initialcharging and the hot metal addition averaging about forty-five minutesand the refining period averaging about two hours and fifteen minutes.When this performance is compared to operation of the same furnaceaccording to normal oxygen practices the great advantages obtained bynovel process become manifest; with the normal oxygen practice heats ofabout six hours were required, the time between initial charging and hotmetal addition being about two hours and the refining time about fourhours.

In view of the complex nature of the physical change and chemicalreactions that take place during a heat in an open hearth furnace it isnot possible to ascertain positively the reasons why the greatadvantages are obtained by the present process. In any event, theobtaining of such advantages is possible by the discovery that hot metaladditions need not be postponed until the charge ltl attains criticalcharacteristics accompanied by a substantially uniform temperaturethroughout the charge but may be made after a predetermined quantity ofheat is absorbed by the charge without regard to the distribution ofsuch heat throughout the charge. In conventional open hearth furnaces towhich the presently described embodiment relates, it is necessary tobank the furnace doors before hot metal additions and accordingly therewould be no apparent advantage to supply to the charge the necessaryheat units for hot metal additions prior to completion of the chargeeven though the unique character of the oxyfnel burners would permit theobtaining of that result. Thus, in the present embodiment it is onlynecessary for optimum performance to apply to the charge the necessaryheat units for hot metal additions at the time the ch ge is complete. Inlater described embodiments which may be considered as involving furthermodifications of conventional open hearth furnaces, it is practicable tosupply to the charge the necessary heat for hot metal additions, and toadd the hot metal, before the solid charge is complete, or, as a matterof fact to adopt a procedure in which solid charge and hot metal aresimultaneously introduced into the furnace. Moreover, in accordance withthe present embodiment, at the bcginring of the refining stage thematerial in the furnace has absorbed a greater number of heat units thanwould be the case at the corresponding point of a heat according toconventional practice. The presence of additional heat in the charge,not only at: the beginning of the refining period but also at leastthroughout a substantial portion of the refining period, is believed toresult in more rapid decarburization and hence the heat may attainproper temperature and composition for tapping at an earlier timefollowing the hot metal addition. Another factor influencing theobtained decrease in the refining time results from the novel step ofcharging hot metal at a time when the charge is at a substantiallynon-uniform temperature, that is, when portions of the scrap immediatelybelow the Oxyfucl burners are at a very high temperature relative toother portions of the charge. Charging of hot metal under theseconditions results in the formation of a foamy slag. The problemsattendant the presence of a foamy slag in conventional operation of openhearth furnaces are not involved when practicing the present embodimentin view of the relatively great quantity of heat absorbed by the charge,or available for absorption, and it has been discovered that thepresence of a foamy slag permits the use of higher oxygen flow ratesduring the refining period, as compared to permissible flow rates underconventional practice. In actual operation of a 200 ton open hearthfurnace according to the present method oxygen flow rates through eachof the two oxy-fuel burners in excess of 45,000 cubic feet per hour wereemployed. Such oxygen flow rates in the same furnace when operatingaccording to conventional practice would result in excessive splashingand resulting roof damage and accordingly could not be used. Thus, thehigh heat content of the charge at the beginning of the refining stageand the presence of a foamy slag are two of the factors which make itpossible to reduce the refining period according to the novel process.

It is understood, of course, that in order to achieve the fulladvantages obtainable by practicing the novel proc css it is necessarythat the solid charge be completed as rapidly as possible and if thetime required for the solid charging is slow it is possible that thecharging time may be greater than the time required to introduce therequired heat units into the charge. As mentioned above the presentprocess was practiced in a 210 ton open hearth furnace employing tworoof-mounted oxy-fuel burners while employing normal charging techniquesand the solid charging was completed within fortyfive minutes at whichtime the furnace was in a condition to receive the hot metal additionsand [low of fuel to the oxy-fuel burners could be terminated. However,in open hearth furnaces of greater capacity, for example 500 tons, it isconceivable that unless rapid charging techniques are employed therequired heat units may be to the charge before the solid charging iscompleted. In such a situation, although the hot metal would be added atan earlier time as compared to conventional practice and the refiningtime shortened, the full advantages obtainable from the present methodcould not be realized without employing a more etficient chargingtechnique.

The 200 ton open hearth furnace operated in accordance with the presentprocess employed end wall burners fed with Bunker C 01] and oxygenaccording to conventional practice. Two oxy-fuel burners, mounted in theroof of the furnace for heightwise adjustment, were fed with natural gasand oxygen of about 99.5% purity and each included a discharge endhaving six one-half inch diameter openings, disposed at 30 relative tothe longitudinal axis of the burner. During the scrap charging thedischarge ends of the burner were located at least two feet above thescrap, and as the scrap melted the burners were lowered to maintain suchspacing. After the hot metal addition and the beginning of the refiningstage the discharge ends of the burners were lowered to a position aboutfour inches above the bath. The following examples comprise dataobtained during heats of the open hearth furnace described above inwhich the oil is rated at 165.000 B.t.u./got, the natural gas rated at1,000 B.t.u./M c.f.; the oxygen was of a purity of 99.5 percent, and inwhich the natural gas consumed is indicated in equivalent gallons of oilbased on 150,000 B.t.u./gal. for oil:

4,800 pounds metal.

Oxygen, oil and natural gas consumption A. From start of charge to startof hot metal addition:

End wall burners Oil224 gallons or 38,960,000 B.t.u. Oxygen-noneOxy-fuel burners- Natural gas-403 gallons or 15,450,000 B.t.u.Oxygen-51,450 cubic feet B. From start of hot metal addition to tap:

End wall burners- Oil-653 gallons or 104,445,000 B.t.u. OxygennoneOxy-fuel burners Natural gasnone Oxygen-139,650 cubic feet CARBONREDUCTION RATE Minutes after hot Oxygen flow Ore addition metal additionPercent carbon oxy-l'nei (pnunds) burners (c.f.h.)

RATE OF TEMPERATURE RISE CIIRONOLOUICAL HEAT LOG Minutes before hotEvent metal addition 38 Oxy-fuol burners on. Oxygen, 45,000e.t.h.,tburnvr and natural gas 42,300 c.[.li. through burners; oil, 10g.]1.l]l. nir, 080,000 0.1.11. 36 Start charge.

. Finish charge.

Oxyluel burners lowered to 4' above scrap.

.. Bank doors.

Oxy-iuei burners lowered to 3' above scrap.

.. Start hot metal addition. Natural gas 00 on cry-fuel burners.

Finish hot mot-a1 addition. Oil increased to 112 gum.

Oxygen to cry-incl increa ed 47,000 c.f.h. and oxy-iucl oued 445" aboveslag.

Carbon 1.005;}. Temperature 2,725 F.

. Oil decreased to 5 g.p.1n., air 3" 34 box ore (1,000 pounds) ad boxore (1,000 pounds) ad 56 box ore (2,000 pounds) Bl'lt ,0.

Red fumes coming [rom stuck, some as when 25,000 c.i.h.

O lance was used. Carbon 1.15%. Oil reduced to 1.56 g.p.in., air;520,000 c.t'.h. Temperature 2,820 One box are (4,000 pounds) added. Oilincreased to 6 gpm. Temperature 2,805 I Carbon 0.20"{ (hath clear andsettled).

Bath fiat ti.e., loss than 0.07% C.). Temperature 020 1 Toniperatum-1340 F.

. 0x1 gen turned off city-fuel burners.

Tap (heat broke out, through tap hole).

EXAMPLE H Furnace charge:

1 3,000 pounds metal.

Oxygen, oil and natural gas consumption A. From start of charge to startof hot metal addition:

End wall burners- Oil-321 gallons or 52,965,000 B.t.u. Oxygen9,500 cubicfeet Oxy-fuel burners:

Natural gas187 gallons or 28,050,000 B.t.u. Oxygen33,150 cubic feet B.From start of hot metal addition to:

End wall burners:

Oil-935 gallons or 154,275,000 B.t.u.

Oxygen-44,500 cubic feet Oxy-fuel burners:

Natural gasNne Oxygen-477,975 cubic feet (A RTBON REDUCTION RATE 1 2EXAMPLE ilI Furnace charge:

Minutes after lint metal addition Percent carbon oxy- Oxygen ilow lburners Kill.)

1 3,000 pounds metal.

RATE OF TEMPERATURE RISE Minutes after but Temgepraturo,

Burner oil flow Oxygen flow End wall burners- Scrap- No. 1 bales pounds23,000 Slab ends d0 115,000 Hot metal do 204,000 Lime d0 8,000 Furnaceadditions:

Ore pounds 6,000 i Total metal (furnace charge, furnace additions) Oreaddition pounds 349,200 fuel (pounds) fotal ingot Weight d0 269,401Skull 2,000 4,591 275,992 14,000 1,501) Yield "percent" 76.84 Productionrate tons/hour 56.60

Oxygen, oil and natural gas consumption A. From start of charge to startof hot metal addtion:

metal addition (g.p.ni.) oxyfuel I burners -l O1l301 gallons or49,665,000 B.t.u.

Oxygen10,000 cubic feet E- Oxy-fuel burners a, i 2.740 a 04,000 Naturalgas-142 gallons or 21,300,000 B.t.u.

g Oxygen-34,800 cubic feet @1830 s 041000 13. From start of hot metaladdition to tap: 3,550 5 14,000 End wall bnrners 2, 900 6 04, 000

O1l-886 gallons or 146,190,000 Btu. Oxygen9,500 cubic feet CURONOLOGIGALHEAT LOG oxy'fuel burners:

Natural gas86 gallons or 12,900,000 Btu. -J I Minum Oxygen188,625 cubicfeet before but Event metal addition Oxy-iuel burners on. Oxygen 45,000e.t.li./burner, natural 40 gas 5.8 equivalent g.p.ni. burner. End wailburner oxygen at 25,000 c.f.l1. oil, 11 g.p.m., air

emcee 0.1.]1, Ftart charge. Finish charge. Fturt banking doors. Finishbanking doors. Reversal time decreased from 6 to 4 minutes. Natural meall oxy-iuel burners. Htai't hot nietal. Oxygen ell end wall burners.Increase oxygen to 47,000 e.f.li.,oxy-iuel bu rner. Finish hot metal.Oxy-iuel burners positioned approximately 0" above slag. Oxygen on endwall burners at 25,000 c.i.ll.; oil 11 g.]J.in.;

air 97 v,000 bill. 01) Steel leaking through tap hole. 'lnp hole seemsto be frozen. Lnr amount of red fumes earning l'roin stack. V v w 0A3gen all end wall burners; oil reduced to 9 guru; air UN RED UCTION RATE050,000 chili. if at. 1 (urban IH 'T. g c F Minutes after liot Oxygen(low Ore addition 051 iduppd (O 5 metal addition Percent carbon (pounds)Carbon 3.30%.

Slart flush.

Temperature 2,GT5 F.

Carbon 1.875%.

Temperature 2,740 I".

Oil decreased to 2 com.

lg llOX ore (1,500 pounds) added.

1% or (4,500 pounds) added. 011 inc-rel d to S g mu.

Carbon 0.625%.

Temperature 2,7?0 1.

Temperatur 2,830 P.

Carbon 0.24"}.

Oil reduced to 0 an. 1.

Temperature 2 580 f Carbon 0.11%. Oil increased to 8 gpm. Spar additions(5-10 shovels).

tapping. Temperature 2,000 F. Start actual tap. 'Iup hole frozen.

"5; temperature 12,700" F.

Oxygen to ext-fuel burners decreased to 20,000 c.l.li./

Iuu'uer due to diiiiculty in tapping.

Readyto tap but dillleulty with the tap 11010 prevented Start steelflowing through tap hole.

OXY-IUE] burners (e.t.h.)

2. 82 90, 000 2. 27 00, 000 1. [i8 96, 000 1. 20 I6, 000 (I. 20 96, 0000. 10 96, 000

RATE OF TEMPERATURE RISE Minutes after hot Temperature, Burner oil flowCIIRONOLOGIC'AL HEAT LOG Minutes before but Event metal addition Naturalgas on north burner at 31,500 0.1. Start charge.

at rate of 25,000 c.f.h. Air 1,000,000 c.i.h. Finish charge. Start tobank doors. Lower oxy-iuel burners to 3-4 above scrap. Start hot metal.Air decreased to 860,000 c.i.h. Start second ladle hot metal.

20,000 c.f.h. Natural gas of! oxy-fuel burners.

pile under oxy-fuel burners.

Oil reduced to 6 g.p.m. Carbon 2.82%.

Oil increased to 8 gpm. Temperature 2,500 F. Carbon 2.72%.

Flush started. Temperature 2,590 F. Temperature 2,630 F.; Carbon 1.68%.Temperature 2,670 F. Oil reduced to 6 ggm. Carbon 1.20%; Fe 33.55.Decrease oil to 3 gpm. Temperature 2,740 F. Add one box ore; foamy slagflushed. Oil increased to g.p.m. Temperature 2,740 P.

Carbon 0.26; FeO 26.21. Spar addition (shovels). Carbon 0.10.Temperature 2,815 F. Increased oil to 8 g.p.m. Temperature 2,865" F.Tap.

Oxygen on oily-fuel burners at 45,000 email/burner.

Natural gas on south burner at 25,000 c.i.h. South burner on later thannorth burner due to minor delay. Oil increased from 4 to 12 g.p.m.Oxygen on end wall burners Finish hot metal. End wall burner oxygenreduced to Natural gas on oxy-iuel burners again due to large scrapNatural gas off oxy-fuel burners; oxy-i'uel burners lowered to bath;oxygen, 48,000 c.i.h. pcr oxy-luel burner. Oxygen 011 end wall burners;oil reduced to g.p.m.

1 2,400 pounds metal.

Oxygen, oil and natural gas consumption A. From start of charge to startof hot metal addition:

End Wall bnrncrs Oil-477 gallons or 78,705,000 B.t.u. Oxygen-42,000cubic feet Oxy-fuel burners Natural gas-494 gallons or 39,456,000 B.t.u.

Oxygen-65,525 cubic feet B. From start of hot metal addition to tap:

End wall burners- Oil-l,l29 gallons or 186,285,000 B.t.u.

Oxygen3,500 cubic feet Oxy-fuel burners-- Natural gas-58 gallons or8,700,000 B.t.u.

Oxygen2l4,350 cubic feet CARBON REDUCTION RATE Minutes after hot Oxygenflow Ore addition metal addition Percent carbon oxy-fuel (pounds)barriers (c.i.h.) o

RATE OF TEMPERATURE RISE Minutes after hot Temperature, Burner oil flowOxygen flow metal addition F. (g.p.m. oxy-iucl burners (c.f.h.)

2, 480 8 98, D00 2, 5'30 5. 8 as, 000 2, 010 6 t0 8 98, 000 2, 080 8 08,000 2, 715 8 98, 000 2, 780 8 to 0 )8, 000 2,810 6 to 5 08, 000 2,880 598. 000 2,930 5 98, 000

CHRONOLOGICAL HEAT LOG Minutes bOlOl'G hot Event metal An additionOxy-fucl burners on at 45,000 c.i.h. burner and total 59,400

c.i. h. natural gas.

Oil 12 g.p.m.; end wall burner oxygen at 20,000 c.i.h.

North oxy-luel burner lowered to both. Oxygen flow 40,000

c. l'.h./o:ry-fuel burner. Oxygen oil end wall burners.

South oxy-tuel burner lowered to bath (delay caused by snagged cable).Oil reduced to 10 gpm. Carbon 2.770%. Oil decreased to 8 g.p.m.; twominute reversals. Good flush started. Oil increased to 10 g.p.m. Carbon2.424%. Temperature 2,480 F. Oil decreased to 3.5 g.p.m. Oil increasedto 5 g.p.m.; tour minute reversals. Oil increased to 0 g.p.1n.Temperature 2,530 F. Oil increased to 8 gpm. Temperature 2,010 F. Carbon1.388%. Temperature, 2,0S0 F. Temperature 2,715 F. Carbon 1.012%. Oildecreased to 6 g.p.m. Temperature 2,780 F. box ore added followed byheavy flush. Oil decreased to 5 g.p.m. Temperature 2.810" F. Carbon0.584%. 1000 ore added followed by heavy flush. Carbon 0.252%.

7 Temperature 2,880 F.

Spar addition (shovels).

Carbon 0.009%.

Temperature 2,030 F.

Oxygen ofi south oxy-[ucl burner.

Oxygen otl north oxy-i'uel burner.

Oxygen, oil and natural gas consumption A. From start of charge to startof hot metal addition:

End wall burners-- Oi1-502 gallons or 82,830,000 B.t.u. OXygen-13,000cubic feet Oxy-fuel burners Natural gas229 gallons or 34,300,000 B.t.u.Oxygen-57,300 cubic feet 13. From start of hot metal addition to:

End wall burners Oil-1002 gallons or 165,330,000 B.t.u. Oxygen8,500cubic feet Oxyfuel burners Natural gas-52 gallons or 7,800,000 B.t.u.Oxygen-210,150 cubic feet CARBON RED UGTION RATE Minutes after butOxygen flow Ore addition metal addition Percent carbon oxy-fuel (pounds)burners (c.f.h.)

RATE OF TEMPERATURE RISE Minutes after hot Temperature, Burner oil flowOxygen flow metal addition F. (g.p.ru.) cry-fuel burners (0th.)

CHRONULUUXCAL HEAT LOG Minutes before but metal addition Event Oily-fuelburners on at. 45,000 c.i,h., oxy-fuol burner; natural gas 00w 3 gum;oil 0 01.11.11].

Start charge.

End wall burner oxygen at 20,000 e.t.li.; oil 12 gums, 11

minute reversals.

Finish charge.

etart blinking doors.

Finish banking doors.

4 minute reversals.

Start hot metal (scrap very hot).

Lower oxy'luel burners to 3' above scrap.

Finish hot rnctul.

Natural gas oft oxy-tuel burners.

Oxygen of! end well burners.

Oxy-fuel burners oxygen at 47,000 e.f.li,/ox1, -[uel burner.

Oxygen on end wall burners at 10,000 clti. to melt ends.

Oxygen 00" end wall burners.

Oil at 10 gum.

Carbon 2.107%.

Oil reduced to 5 g.p.rn.

Start llush on reversals.

Carbon 2.552%.

Oil reduced to 4.0 guru.

Temperature 2,590 F.

Oil reduced to 2 gout.

Start good flush.

Oil 00; and draft both ways.

Start reversal. No oil,

Carbon 1.772%.

'lempernture 2,060 F.

Oil on at 4 gum.

1 box ore added followed by heavy flush.

Oil increased to 5 g.p.rn.

Carbon 1.210%.

'lemperature 2,720 F.

Start good flush.

Carbon 1.00%.

Oil oil; draft both ways.

Draft on.

)4, box ore added.

Oil on at l gnm.

35 box ore added.

'lern iernture 2,735 F.

Oil increased to 10 gpm.

Carbon 0.25%.

Spar addition.

Temperature 2,795 F.

Oil decreased to 0 gum.

Oil decreased to 5 gum.

Temperature ?,855 F.

(Durban 0.075%.

Oil increased to 9 g.p.rn.

Oxygen flow through north oxy-luel burner decreased to 35,000 elh.

Temperature 2,800 F.

Tap.

EXAMPLE VI Furnace charge:

Scrap- No. 1 bales pounds 69,000 Slab ends -do 113,000 Hot metal do213,000 Lime do 8,200 Furnace additions- Butts do 23,000 Ore do 6,000Ladle additions- Total metal do 2,500 Total metal (furnace charge,furnace and ladle additions) pounds 424,100 Total ingot weight do345,400 Butt do 2,000 Total tap weight -do 347,400 Yield "percent" 81.90Production rate tons/hour 55.18

3,000 pounds metal.

Oxygen, oil and natural gas consumption A. From start of charge to startof hot metal addition:

End Wall burners- Oil-583 gallons or 96,195,000 B.t.u.

Oxygen-1,900 cubic feet Oxy-fuel burners- Natural gas-342 gallons or51,300,000 B.t.u.

Oxygen64,050 cubic feet 17 i From start of hot metal addition to tap:

End wall burncrS Oill,009 gallons r 166,485,000 B.t.u. Oxygen-4,250cubic feet Oxyfuel burners- Natural gas27 gallons or 4,050,000 Btu.Oxygen222,375 cubic feet CARBON REDUCTION RATE Minutes after hot metaladdition Ore addition (pounds) i Percent carbon i burners (0th.)

2. til 00. 000 2.

RATE OF TEMPERATURE RISE (I [I RONOLO tiICAL llEslI LO Cr Minutcs batorchot nictal addition Event Oxy-tuul lnirncrs on with oiygcn til 38,000stir/burner and natural [HIS at 7.3 gpm. total.

St t charge.

()xyqen on and wall burner at 20,000 eih.

on at 11.9 g.p.m.; [1.2 minute IUVCISltlS.

Oxy-incl burner oxygen increased to 40,000 c.i.h., burncr and naturalgas decreased to 7.1 g.p.ni. total.

Finish charge.

Lower oxy-iucl hlllili! to approximately 3% above both.

Finishing banking of doors,

Uil increased to 12.4 g.p,in.; 4.8 minute rcvcrsuls.

St art hot inctul.

Natural gas oli' 0i oxy-i'ncl hurnrrs.

OsyJuel lJLlltlUl' oxygen increased to 40,506 nth/burner.

Finish hot metal.

Oxygen oil and wall hurncrs.

Oil dccrcnscrl to it) g.pini.

Carbon 2.01%.

Tmnpt Light flush; lunin i in: rapidly. Oil rlccrcnsu l to 3.l gum,'icrnpcralurn 2,020 I". Carbon 1.9001, Heavy ilu h. 00 :0 bloom hullsadded. Carbon 1,62%. Tuninnratnrc 2,070 F. South? bloom butts added. tinivy [lush at #5 and #3 doors. ()il oiT and wall burners; both diinipcrsopen. 7 il lfitttt bloom butts added. and are added.

i Oil on at 5 ppm; 5 minute rcversals.

S1); everal shovels; oil on lit 7.4 gum.

* lllOl soft, hath solidified inside #3 and AM doors.

shovels. l to 0.2 'inmpcmturc 2,800"

tit

One of the advantages of the present invention is that it cnablcscomplete control of the furnace atmosphere, even to the point of totallyeliminating feed air and introducing substantially all of the furnaceatmosphere through the jet burners. In view of the fact that air isnitrogen, there is thus avoided the problem of heating up great massesof nitrogen and recovering its heat content, so that the total quantityof gases passing through the furnace as furnace atmosphere is enormouslyreduced, as is also the need for heat exchange equipment. Indeed, theelimination or substantial elimination of nitrogen from the burner flameby feeding oxygen of a purity of or greater to the oxyfucl burnerenables the use of a very much smaller flame to supply the same heatvalues or even substantially to increase the heat supplied to theoperation by the flame as compared to conventional practice; and this inturn makes it possible to play the smaller flame on the material from ashort distance, thereby to transfer substantially all the heat of theflame to the material by convection rather than by radiation, with theaccompanying reduction in heat losses and furnace lining damage referredto above. The possibility of eliminating end wall burners and of greatlyreducing the size of the flame also makes it possibte radically to alterthe construction of the furnace so as to provide a very much simplerstructure.

In view of these new considerations, the structure of furnaces such asthe conventional open hearth furnace can advantageously be furthermodified as shown in the embodiment of FIGURES 4 and 5. It will berecognized that the structure of FIGURES 4 and 5 maintains the overallconfiguration of an open hearth furnace according to FIGURES 1, 2 and 3,but with three princi al modifications: the end wall burners areeliminated entirely; the jet devices extend through the roof instead ofthrough the end Walls; and the chcckcr system is eliminated.

Referring to FIGURES 4 and 5 in greater detail, there is shown anelongated furnace of the open hearth type having a bottom 47, a frontWall 48, a back wall 49, and a pair of end walls 51 only one of which isshown. A roof 53 is provided, and the furnace is lined with conventionalfire brick so as to provide a hearth 55 for the reception of a charge ofmaterial, which is shown in the illustrated embodiment during a refiningperiod as a bath of molten metal 57.

A plurality of elongated jet devices 59 is provided, spaced apartlengthwise of the furnace. and each treats the subjacent portion of thebath. They extend through the roof, however, instead of through the endwalls; and for this purpose, mounting means 61 are provided lengthwiseslidably to receive jet devices 59, these mounting means allowingvertical axial movement thereof. Each jet device 59 has a rack 63secured lengthwise thereto and in mesh with a pinion rotatable about ahorizontal axis by manipulation of a hand wheel 65, the pinion and handwheel assembly being carried by vertical slccve 67 in which jet device59 and rack 63 are mounted for vertical sliding movement. Sleeve 67, inturn, is supported by legs on the furnace, directly above mounting means61. By this mechanism, manipulation of hand wheel 65 will raise or lowerjet device 59 as desired.

In order to provide support for this arrangement, a frame 69 of I-beamsis provided, including a plurality of upright stub columns 71 along theend and side walls of the furnace, interconnected at their upper ends bylongitudinal beams 73 and transverse beams 75, the beams 73 and 75carrying on their upper surfaces deck plates 77 apertured for thereception therethrough of the jet devices.

As the jet devices of the embodiment of FIGURES 4 and 5 are notuniversally movable but only vertically adjustable, the flames wouldtend to be concentrated only in a single spot if the lower ends weresimply cylindrical as in the case of the preceding embodiment.Therefore, a flared or bell-shaped configuration is imparted to thelower ends of the jet devices, as best seen in section in FIGURE 6. Asis there shown, each jet device has a conical lower end or nozzle 79,and the central conduit 81 which carries the fuel does not extend downsubstantially below the cylindrical portion of the jet device. Outerconduit 33 follows the upper cylindrical and lower conical configurationof the jet device, and it is between conduits 81 and 83 that the oxygenpasses. The annular passageway bounded by conduit 83 terminates downwardin a plurality of separate, diverging outlets 85. These are directeddownward at angles to the horizontal of substantially greater than Awater jacket 87 comprises the outer shell of the jet devices and isspaced outwardly of conduit 83 so as to provide an upper cylindrical andlower conical water chamber which is divided lengthwise of the jetdevice into two separate portions that communicate only at the lowerend, so as to cause the cooling water to follow the path described abovein connection with FIGURE 1. There is thus provided a device in whichflames issue from nozzle 79 in downwardly divergent relationship so asmore uniformly to distribute the points of contact of the flame with thebath, as indicated by the circles 89 in FIGURE 5.

The atmosphere of the furnace of FIGURE 4 is comprised substantiallyentirely of the gases introduced through jet devices 59 plus the gaseousreaction products of those gases with the impurities or other substancesin the charge. In the case of a steel making operation, for example, inwhich a hydrocarbon fuel is introduced in admixture with oxygen throughthe jets, and in which the material removed in vapor phase from thecharge is considered to be primarily carbon, the furnace atmosphere willhe principally carbon monoxide, carbon di- I oxide and water vapor plusexcess hydrocarbon fuel or excess oxygen. The iron oxide may beconsidered to be in solid phase as smoke. The volume of gases that mustbe removed from the furnace is therefore greatly decreased, and can behandled by a relatively small discharge conducit 78. There is no need toprovide heat exchange checker systems for this relatively small vol umeof gas, and it can be used directly to heat the separate components ofthe fuel or oxygen feed to the jet devices, or to preheat the charge.There is thus provided an arrangement in which conventional furnaceconstruction is greatly simplified by the total elimination of the usualextensive heat exchange systems and gas handling equipment. Of course,the jet devices of FIG- URE 4 could if desired be replaced by jetdevices constructed in accordance with FIGURE 1 and extending throughthe end walls or the back wall.

A less radical departure from present or conventional open hearthfurnace construction is suggested by a further embodiment as seen inFIGURE 7. There, a furnace 91 is shown in transverse cross-section, thefurnace having a rear wall 93 and a hearth 95. The checker system forthe furnace is preserved, but in modified form. Therefore, at the endsof the furnace, the gas passageways communicate between the interior ofthe furnace and a slag pocket 97 which in turn leads to checkers 99. Thecheckers 99 communicate with the ambient atmosphere through flues 101.

Specifically, the modification of FIGURE 7 differs from conventionalconstruction in two respects: (1) a substan tial portion of the heatrequirements of the operation is supplied by means of oxy-fuel jetdevices of the pres ent invention, extending through the roof or the endwalls or the back wall; and (2) a portion 103 of the checkers iseliminated and the wall 105 of the checker chamber which serves as thebulkhead is correspondingly changed in position as seen in broken linesin FlGURE 7 so as to provide a checker chamber of reduced volume corresponding to the reduction in the quantity of heat exchange materialtherein. It will be understood that the elimina- 20 tion or substantialreduction of the nitrogen in the fun nace atmosphere by the use ofoxy-fuel mixtures of the present invention enables Such provision ofsmaller and less expensive heat exchange systems. Thus, the embodimentof FIGURE 7 is a step midway between the em bodiments of FIGURES l and4.

A highly advantageous further embodiment of the invention is shown inFIGURE 8. As is there shown, a furnace is provided in the from of aconverter 109, uprighl crucible, having downwardly dished bottom 111 andcyiindical side walls 113 which terminate upward in u conically upwardlyconverging top. Side walls 113 carry diametrically opposed axiallyaligned trunnions 115 mounted for rotation in fixed supports so thatconverter 109 may be rocked about a horizontal axis.

Extending down into converter 109 and terminating only a short distanceabove the bath therein is an elongated jet device 117 having avertically disposed end section 119 substantially within the converterand a horizontal base portion 121. Jet device 117 is carried by a sleeve123 releasably clamped to base portion 121 so that upon loosening thesleeve, base portion 121 may rotate therein to enable the verticalsection 119 to be withdrawn from the converter. Sleeve 123, in turn, issupported by a vertical rack bar 125 slidably mounted in a trolley thatrolls on horizontal rails 129. A motor 131 is carried by the trolley anddrives a pinion 133 in mesh with the rack teeth of rack bar 125 therebyto raise and lower rack bar 125 relative to the trolley so as to changethe elevation of jet device 117.

Cooling fluid is supplied to jet device 117 through supply and returnwater lines 135, and the components of the combustible mixture aresupplied to the jet device through fuel and oxygen lines 137, as in theprevious embodiments.

In operation, after the converter of FIGURE 8 has been charged, it isnecessary only to roll the trolley along rails 129 until section 119 ofjet device 117 is directly over the mount of converter 109. Motor 131 isthen actuated to lower the jet device to the desired elevation withinthe converter. If the converter has been charged with scrap or othersolid charge, the lower end of section 119 will initially be higher thanis shown in FIGURE 8[;] [and after] A frer the melting down period iscompleted, motor 131 will again be actuated to lower the jet device tothe position of FIGURE 8 and then at least oxygen is flowed through thejet device 117 to effect the refining. If it is desired to pour off slagduring the heat, the jet device is simply raised and the convertertilted to decant the slag. At the end of the heat, the jet device israised and rolled away, whereupon the refined metal may be tapped froman upright converter or teemed from a tilted converter.

The application of the present invention to converters of the type shownin FIGURE 8 makes possible a great advance in the art of pyrometallurgy,Heretofore. the use of scrap in such converters had been limited forthere had been no commercially practical way to supply the heat neededto enable the use of solid charge material such as scrap or ores or thelike. By the present invention, however, there is provided a means bothfor supplying any portion of or the total heat requirements of theprocess even when a large quantity of scrap is used, and for supplyingany portion of or the total atmosphere requirements of the process,regardless of the nature or configuration of the furnace. Thus, for thefirst time in a converter, it is possible to employ large proportions ofsolid charge materials and thereby obtain the most economical charge.

It is desirable to recover some of what would otherwise be the lost heatvalues of the operation. A further embodiment of the invention, designedfor this purpose, is shown in FlGURF. 9. The modification of FIGURE 9uses the same converter and jet device a in FIGURE 8, so thatcorresponding parts are indicated by primed rcference numerals in FIGURE9. In addition, in FIGURE 9, a preheat chamber 139 is provided which isvertically eiongated and has cylindrical side walls 141 and carries aquantity of charge 143 just suflicient for the next heat, so that thewaste gases from one heat preheat the solid charge for the next heat.The bottom of chamber 139 is closed by a horizontally slidablegas-permeable grating which may be withdrawn to let the charge fall intothe furnace. The furnace gases thus pass through the grating and charge143 and escape from the top of chamber 139 by way of discharge conduit147, whence they may be used to preheat the oxygen and fuel or may bedischarged to the atmosphere. In any event, by this means, the heatvalues of the exiting furnace gas are recovered.

As the gases escaping from the furnace may not be fully burned, furtherheat values are recovered from these gases by supplying air through ablower 149 to an annular bustle pipe 151 that surrounds the lowerportion of side walls 141 and communicates with the interior of chamber139 through holes through those side walls. The charge to chamber 139 issupplied by means of a hopper 153 which stores a quantity of solidcharge such as scrap or ore or lime or limestone or the like. Adischarge assistant is provided for the bottom of hopper 153, in theform of a horizontally reciprocable plunger 155 which advances materialfrom the hopper through a discharge conduit 157 and thence into chamber139. The angle of repose of the charge in discharge conduit 157 is suchthat charge material does not pass from hopper 153 to chamber 139 in theabsence of movement of plunger 155.

In order to assure that a maximum proportion of the gases escaping fromthe furnace passes through the charge to preheat the charge, a removableadapted shield may be provided to form a confined gas passageway betweenconverter 109' and chamber 139. This adapter includes a pair of opposedgenerally semfcylindrical adapter halves 159 which have confrontingcontiguous vertical edges, the edges to the right of FIGURE 9 beingrecessed with confronting slots 161 to provide a vertical elongatedopening in which jet device 117 may be moved. A shield 163 fixed tohorizontal portion 121 of jet device 117' moves with the jet device andcloses slots 161 in all positions of the jet device relative to theadapter. On the other side of adapter halves 159, to the left of FIGURE9, there is shown the mounting for halves 159 by which they swing inclamshell relationship. Both halves 159 are Thus, when it is desired toremove jet device 117' from converter 109', it is necessary only to openhalves 159 by manipulation of. rods 167, raise the jet device byactuation of motor 131' in an appropriate direction, release sleeve 123'and move trolley 127' lengthwise of tracks 129' to slip the jet deviceout from under the fixed preheat chamber 139. For adjusting theelevation of the jet device with the adapter halves closed, as betweenvarious stages of a heat, it is necessary only to actuate motor 131' inthe appropriate direction, whereupon the jet device moves vertically inslots 161.

Still another of the many forms of furnace in which the presentinvention may be practiced is the electric arc furnace. FIGURES l0 and11 show a direct-arc electric furnace 169 modified according to thepresent invention. As is usual in such furnaces, the furnace structureincludes a generally circular bottom 171, a cylindrical side wall 173and a domed roof 175. Roof 175 may be removable for top charging, ifdesired, or charging may be effected through one or more charging doors177. A tapping spout 179 is provided for discharging slag when thefurnace is rocked on trunnions (not shown) about at horizontal axis, orfor teeming the molten charge 181 into molds. Thus far, the structure ofFIGURES 1t) and 11 is merely conventional electric furnace structure.

Electric furnace structure is ordinarily further charao terizcd by theprovision of carbon or graphite electrodes extending through the roof;but in the present invention, one or more or all of these electrodes arereplaced by oxyfuel delivery devices as previously described or suchoxyfuel delivery device or devices may be added. Of course, if all theelectrodes are replaced with jet devices, the furnace is no longer anelectric arc furrace. Therefore, the embodiment of FIGURES l0 and 11should be considered not so much as improvement in electric arc furnacesas a means for using existing electric furnace capacity for the practiceof the present invention.

In accordance with the invention, the structure of FIG- URES 1t) and 11dilfers from conventional electric furnace construction in that insteadof electrodes, jet devices 183 extend through the roof through theelectrode openings therein and into the furnace to a point a shortdistance above charge 181. Jet devices 183 are the same as jet devices59 of FIGURE 4, and are mounted on roof 175 and are verticallyadjustable relative to the charge in the furnace by means of mountingmeans 185 identical to the corresponding mounting means of FIGURE 4. InFIGURES l0 and 11, all three electrodes are shown replaced by jetdevices, but it will also be understood that in furnaces having multipleelectrodes, less than all the electrodes may be replaced.

The principles of the invention will be more fully understood from aconsideration of thc manipulative steps associated with an individualheat. For purposes of illustration, the example of an open hearthfurnace used for steel production will be considered, it being expresslyundcrstood that substantially the same manipulative steps apply to theproduction of other refined metals from which substances other than orin addition to carbon are removed during refining.

Accordingly, in connection with the embodiment of FIGURES l, 2 and 3,the furnace is charged with limestone, ore and scrap, and atomized fuelis fed to burner 19 in a conventional manner so as to produce arelatively large, low velocity, low temperature flame. After the scrapcharge has begun, for example after about onefourth of the scrap ischarged, oxygen and fuel are fed through the jet device to within thefurnace to form a relatively small high velocity high intensity flame atthe discharge end of the jet device, This flame is disposed beneath thelarger burner flame, and the burner flame, at substantially lowertemperature, in effect insulates the root from the jet flame, asdescribed above. Using natural gas as the fuel and assuming forsimplicity that natural gas consists of methane, the oxygen fuel ratiois regulated to form a stoichiometric mixture of two parts of oxygen toone part of methane thereby to provide maximum heat input.

The jet device is moved so that its flame end is only a short distancefrom the solid charge; and with the flame playing at relatively highvelocity and temperature di rectly on the charge within the confines ofthe contour of the charge, it is moved about the surfaces of the chargewithin the confines of the contour of the charge in such a manner as tomelt the scrap within the shortest period of time. Movement of the jetdevice may be programmed by automatic control of the mechanism forimparting different movements to the jet device, or it may be movedunder manual control at random according to the option of the operator.During this stage, the fuel-oxygen ratio is usually selected for nearlymaximum heat input and for providing an oxidizing atmosphere in thefurnace to oxidize scrap to the desired degree during the melt-downperiod. However, it is possible to vary this ratio so as to increase ordecrease the oxidizing tendency of the mixture, or even to provide aneutral or reducing atmosphere, depending on the quality and makeup ofthe scrap in the furnace. Generally. fine scrap requires reducing oxyfuel mixtures, while heavy scrap such as ingot butts or slabs rcquircsmore oxidizing oxy-fuel mixtures.

When the charge is fully liquid, the play of the relatively small,short, high velocity and high temperature flame on the now-liquidsurface of the charge may be continued, with the jet tip only a shortdistance from the surface of the charge and the axis of the jet flame atan angle no less than about 25 to the surface of the bath and the highvelocity flame parting the slag and directly contacting the moltenmetal, until the end of the refining period.

Upon hot metal addition, slag will form over the bath but its presencewill not decrease heat transfer from the flame, since the momentum ofthe flame at the discharge end of the jet device is suflicient to blowthe slag from the surface of the metal and allow the flame to impingedirectly on the metal. Thus, development of a foamy slag presents noproblem in practicing the present invention and there is no necessity,as in conventional operations, to cut back on the fuel input to thefurnace until the foamy slag condition is corrected.

In those instances in which the jet device is mounted through an end orside wall, it is also advantageous to continue movement of the jetdevice throughout the period during which the charge is liquid, as thisaugments the natural circulation of the bath and further reduces thetotal time of the heat.

It maximum heating effect is required, oxygen and fuel together may becontinuously fed through the jet device during the heat and on into therefining period. As the metal bath may require, the fuel may bedecreased and finally cut off to feed oxygen alone through the jetdevice for the last stages of refining. Of course, as men tioned above.abnormal conditions may be corrected by altering the fuel-oxygen ratiofrom this predetermined pattern.

Thus, a further feature of the present invention is the possibility ofutilizing oxy-fuel flame during the refining period of a heat such thatthe temperature and the reaction between oxygen and the impurity in thebath can be most effectively controlled. Thus, the refining period s ineffect begun much earlier in the present invention than in processesemploying a conventional oxygen jet such as a roof lance.

As the operations in which the present invention is useful are primarilymethods for controlling oxidation reactions so as to remove metalloidsand to apply proper heat input to metal baths, a very important featureof the present invention resides in the fact that this inventionprovides for the first time an instrumentaiity for performing both ofthese two functions. Thus. the present invention is characterized byapparatus which may be manipulated both to control heat input and toremove impurities, either sequentially or concurrently.

Further possibilities of the present invention involve the introductionof materials other than oxygen and fuel through the jet devices. Forexample, in the case of steel making. powdered lime or ore may beintroduced in suspension in the oxygen stream.

The manipulative steps described above are also appli cable to theembodiments of FIGURES 4, 8, 9 and it), except of course that there isno burner flame apart from the flames issuing from the jet devices, andapart from the fact that the jet devices are not universally movable butrather are vertically adjustable along their axes, Thus, in the case ofthese latter embodiments. the jet devices will be used in relativelyelevated positions during melt ing down or other initial stages of aheat, and will be used in relatively lowered positions during refiningor other stages of the heat during which the charge is principally inliquid phase. in the case of the embodiments of FIGURES 8 and 9, inwhich the charge in hopper 153 is preferably of uniform composition andin which it is obviously desirable to avoid the introduction of chargesof different compositions by means of chamber .139, the advantages ofintroducing a portion of the chnrgc in solid phase in stupcusion in thegaseous material passing 24 through the jet device will be particularlyapparent, for in this way the composition of the charge may be variedaccording to the stage of the heat.

In the particular case of decarburization during steel making, when anoxygen is used, the reaction proceeds as follows:

However. with the flame of the present invention conitlcring. forexample, methane to be the fuel, it is believed that the followingreaction takes place:

and then. in thc bath, the further reactions occur as follows:

The foregoing reactions indicate that with pure oxygen, one mol ofoxygen removes two mols of carbon while with an oxygen-methane flame,two mols of oxygen remove three mols of carbon. There is thus aconsiderable difference between the introduction of an oxygen jet forrefining purposes and the practice of the present invention in which thefuel and the oxygen are admixed together and burned to produce a flamewhich is used to perform a portion of the refining operation. The flameof the present invention removes less carbon per mol of oxygen and hencegives a much less violent reaction than an oxygen jet. This oxy-fueltechnique. by lowering the carbon reduction rate, substantially adds tothe heat in put to the bath without reducing carbon too rapidly, withthe result that the temperature and carbon level in the bath can be moreclosely controlled. In any event, it is evident that by the practice ofthe present invention the total time per heat is greatly reduced.Moreover, comparable advantages are obtainable in the case of othermetals containing other impurities to be removed during refining.

As mentioned above, it is also contemplated by the present invention toadjust the oxygen-fuel ratio of the oxygen and fuel fed to the furnacethrough the confined path provided by the jet device in order to controlthe atmosphere and temperature of the furnace in such a manner as tomeet specific requirements during various stages of a heat. For example,when the application of maximum heat is desired the oxygen-fuel ratio isadjusted to provide a stoichiometric mixture, while if maximum heat isnot required the ratio is adjusted to provide an abundance of oxygen orfuel depending upon whether an oxidizing or non-oxidizing atmosphere isdesired. Where the oxygcn-fuel ratio does not provide a stoichiometricmixture, the extent the ratio departs from a stoichiometric mixture,whether there is an excess of oxygen or fuel, will depend upon specificfurnace requirements.

It has been determined that the ratio of oxygen to fuel may bemaintained in a range of about 0.7 of a stoichiometric mixture to about1.8 of the stoichiometric mixture and provided the necessary control oftemperature and atmosphere during the stages of an open hearth processwhen fuel is required through the jet device. The range of oxygen ratiosto one part of fuel for various fuels in accordance with this formulaare as follows:

Range of oxygen Type of fuel: ratios (by volume) )il (litnlhtt c t-u.fm'gul 300-451) For each fuel. combustible gas or hydrocarbon oil, theoxygen ratio providing a stoichiomctric mixture will com prise thepreferred ratio when maximum heat is desired.

The present invention may be practiced by employing pure oxygen orimpure oxygen within limits which may be determined at least in part bythe quantity of heat the charge may adsorb and by the amount of nitrogenthat may intimately contact the bath without adversely affecting desiredcharacteristics of the product. In gen eral, oxygen of a purity abovemay be employed. The purity of the oxygen may be varied throughout theprocess with, for example, oxygen of low purity being employed duringinitial phases of the process when the charge is relatively cold andoxygen of high puriy being used during refining especially when oxygenalone is introduced through the confined path.

As mentioned above the discharge end of the oxyfuel burner may beprovided with a plurality of discharge nozzles positioned about anddisposed downwardly and outwardly relative to the longitudinal axis ofthe oxy-fuel burner. This type of discharge end produces a plurality offlames that impinge upon a substantially circular area located below theoxy--fuel burner and substantially cortcerttric with its longitudinalaxis. in some application of single or multiple oxy-fuel burners mountedin the roof of conventional open hearth furnaces or modified open hearthtype furnaces according to the present invention, it may be desirable toemploy oxy-fuel burners having discharge ends designed to provide aplurality of flames that will impinge upon a non-circular area in orderto apply heat directly to a greater area of the charge without damage tothe side walls. This may be accomplished by positioning the dischargenozzles on the opposite sides of the burner which face the side walls ofthe furnace at a less angle than the other nozzles which generally facethe end walls of the furnace. Also, the discharge end may be constructedso that the discharge opening of the nozzles lie in any desired path.

If desired the oxy-fuel burners may be used in combination with oxygenlances or the oxy-fuel burners may be provided with a separatepassageway for oxygen to provide for simultaneous heating and refining.

Moreover, the concept of feeding the total feed through the oxy-fuelburners may be employed in conventional furnaces with the fuel inputbeing as high as permitted by the existing exhaust system.

From a consideration of the foregoing, it Will be ob vious that all ofthe initially recited objects of the present invention have beenachieved.

It is to be understood that the appended claims are to be accorded arange of equivalents commensurate in scope with the advance made overthe prior art.

What is claimed is:

1. The method of operating a metallurgical furnace of the open hearthtype having a bottom, a roof and side walls defining a zone and havingend wall burners, comprising the steps of operating the end wall burnersand introducing fluid including fuel and oxygen along at least oneconfined path downwardly to within the zone, burning the fuel and oxygenin admixture to form a short flame beyond the end of the confined path,charging solid material including metal into the zone, operating the endwall burners and separately burning the admixture to form a short flamewhile charging the solid material while moving the end of the confinedpath to direct the short flame onto solid material beneath the confinedpath, adding hot molten metal to the zone upon the completion of thecharging of solid material, and thereafter continuing the introductionof at least oxygen through the confined path and directing the resultingstream onto the molten metal to refine the metal of the charge.

2. The process of producing steel comprising charging a. furnace withsolid ferrous metal, [mixing in] feeding through a lance a fluid fueland substantially pure oxygen, causing the lance to direct an oxygenfluid fuel flame downwardly upon the solid ferrous metal from a locationabove the solid ferrous metal while solid ferrous metal is beingcharged, melting a substantial portion of the solid ferrous metal by thefluid fuel oxygen flame emitted by the lance, [shutting the] reducingthe flow f fluid fuel [oil] from the lance while continuing the flow ofoxygen during refining, lowering the lance to a position such that theoxygen flow is discharged during at least a portion of the refiningperiod in the immediate vicinity of the metal bath surface andpermitting the oxygen flow from the lance to lower the carbon content ofthe bath.

3. The process of producing steel in an open hearth furnace comprisingcharging the furnace with solid ferrous metal, mixing in a lance a fluidfuel and substantially pure oxygen, causing the lance to direct anoxygen fluid fuel flame downwardly upon the solid ferrous metal from alocation above the solid ferrous metal while solid ferrous metal isbeing charged, melting a substantial por tion of the solid ferrous metalby the fluid fuel oxygen flame emitted by the lance, charging molteniron into the furnace, shutting the fluid fuel oil from the lance whilecontinuing the flow of oxygen, lowering the lance to a position suchthat the oxygen flow is discharged in the immediate vicinity of themetal both surface, permitting the oxygen flow from the lance to lowerthe carbon content of the bath during a refining period, and controllingthe temperature of the bath during said refining period by the additionto the bath of solid ferrous metal.

4. The process of producing steel in [an open hearth] a furnacecomprising charging the furnace with solid ferrous metal, [mixing in]feeding l/UOtlg/l a lance a gaseous fuel and substantially pure oxygen,causing the lance to direct an oxygen fuel flame downwardly upon thesolid ferrous metal from a location above the solid ferrous metal whilethe solid ferrous metal is being charged, melting a substantial portionof the solid ferrous metal by the oxygen fuel flame emitted by thelance, charging molten iron into the furnace. [shutting the] reducingthe flow of gaseous fuel [off] from the lance while continuing the flowof oxygen [lowering the lance to a position] such that the oxygen flowis discharged in the immediate vicinity of the metal bath surface andpermitting the oxygen flow from the lance to lower the carbon content ofthe bath.

5. The process of producing steel in an open hearth furnace comprisingcharging the furnace with solid ferrous metal and lime, mixing in alance a fluid fuel and substantially pure oxygen, causing the lance todirect an oxygen fluid fuel flame downwardly upon the solid ferrousmetal from a location above the solid ferrous metal while the solidferrous metal is being charged, melting a substantial portion of thesolid ferrous metal by the tluid fuel oxygen flame emitted by the lance,charging molten iron into the furnace, reducing the flow of fluid fuelfrom the lance while continuing the flow of oxygen, lowering the lanceto a position such that the oxygen flow is dis charged in the immediatevicinity of the metal bath surface and permitting the oxygen flow fromthe lance to lower the carbon content of the bath.

6. The process of producing steel in an open hearth type furnace having[end wall] conventional (ml wall burners, comprising charging thefurnace with solid ferrous metal, operating the [end wall] conventionalcm! Walt burners, feeding through a lance a fluid fuel and substantiallypure oxygen, causing the lance to direct an oxygen fluid fuel flamedownwardly upon the solid ferrous metal from a location above the solidferrous metal while the solid ferrous metal is being charged, melting asubstantial portion of the solid ferrous metal by said [end wall]conventional and wall burners and the fluid fuel oxygen flame emitted bythe lance, charging molten iron into the furnace, reducing the flow offluid fuel from the lance while continuing the flow of oxygen, loweringthe lance to a position such that the oxygen flow is discharged in theimmediate vicinity of the metal bath sur-

